Anatomy - Superficial and Deep Muscles of the Back (Tables 1.1 and 1.2)

Which deep muscles are segmentally innervated by dorsal rami?

splenius, erector spinae, transversospinalis

Extends the vertebral column or head/neck

bilateral contraction

Laterally flexes or rotates the head, neck, or trunk

unilateral contraction

“Dorsal Scapular Nerve (C5)” Trio

levator scapulae, rhomboid major, and rhomboid minor (all innervated by C5)

Trapezius attachments

occipital bone, nuchal ligament, C7-T12 spinous processes —> spine of scapular, acormion, lateral 1/3 of clavicle

Trapezius action

elevates, retracts, depresses, and upwardly rotates the scapula

Trapezius innervation

CN XI (Spinal Accessory Nerve) for motor; C3-C4 for proprioception

Lattisimus Dorsi attachments

T7-sacrum spinus processes, thoracolumbar fascia, iliac crest, lower ribs —> intertubercular groove of humerus

Lattisimus dorsi action

extends, adducts, and medially rotates the humerus (“swimmer’s muscle”)

Lattisimus dorsi innervation

thoracodorsal nerve (C6-C8)

What are the scapular retractors and elevators?

rhomboid major, rhomboid minor, levator scapulae

C7-T1 spinous processes —→ medial border of scapula

rhomboid minor

T2-T5 spinous processes —→ medial border of scapula

rhomboid major

Memory hook for spines

Minor is higher (C7-T1); Major is lower (T2-T5). Both retract the scapula.

C1-C4 transverse processes —→ superior angle/medial border of scapula

levator scapulae

Levator scapulae action

elevates and rotates scapula; laterally flexes neck

Memory trick: “Bandage” muscles (superficial intrinsic muscles)

splenius capitis and splenius cervicis

C7-T4 spinous processes/nuchal ligament —→ mastoid process and occipital bone

splenius capitis

T3-T6 spinous processes —→ C1-C3 transverse processes

splenius cervicis

intermediate intrinsic muscles

erector spinae group

Memory trick: order of erector spinae group from lateral to medial is “I Love Spine”

Iliocostalis, longissimus, spinalis

attaches to iliac crest, ribs/costals, cervical vertebrae

iliocostalis

thoracodorsal fascia/transverse processes —→ vertebrae and mastoid process

longissimus

most medial (runs spinous process to spinous process)

spinalis

shared primary action of erector spinae group

bilateral extension of the vertebral column; unilateral lateral flexion

Run from transverse processes below to spinous processes above

transversospinalis group

most superficial of the transversospinalis group; reaches thoracic/cervical spines and occipital

semispinalis

intermediate of the transversospinalis group; spans from sacrum and transverse processes to spinous processes 2-4 segments above

multifidus

deepest layer of transversospinalis group; spans from transverse processes to base of spinous processes

rotatores

Core action of the transversospinalis group

Bilateral extension; unilateral contralateral rotation of the vertebral column

superficial back muscles

trapezius, levator scapulae, rhomboid major, rhomboid minor, and latissimus dorsi

Upper limbs muscles (superficial back muscles BESIDES THE TRAPEZIUS) are innervated by what?

the ventral rami of spinal nerves (brachial plexus branches)

Trapezius muscle is innervated by what?

CN XI